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Solanaceae
Solanaceae, or nightshades, are an economically important family of flowering plants with a worldwide distribution. The family ranges from herbs to trees, and includes a number of important agricultural crops, medicinal plants, spices, weeds, and ornamentals. Many members of the family contain potent alkaloids, and some are highly toxic, but many cultures eat nightshades, in some cases as a staple food. The name Solanaceae derives from the genus Solanum "the nightshade plant". The etymology of the Latin word is unclear. The name may come from a perceived resemblance of certain solanaceous flowers to the sun and its rays. In fact one species of Solanum (Solanum nigrum) is known as the "sunberry". Alternatively, the name could originate from the Latin verb solari, meaning "to soothe", presumably referring to the soothing pharmacological properties of some of the psychoactive species of the family. Solanaceae includes a number of commonly collected or cultivated species. Perhaps the most economically important genus of the family is Solanum, which contains the potato (another common name of the family is the "potato family"), the tomato and the aubergine or eggplant. Another important genus Capsicum produce both chili peppers and bell peppers. The genus Physalis produces the so-called groundcherries, as well as the tomatillo (Physalis philadelphica), the Cape gooseberry and the Chinese lantern. The genus Lycium contains the boxthorns and the wolfberry Lycium barbarum. Nicotiana contains, among other species, the plant that produces tobacco. Some other important members of Solanaceae include a number of ornamental plants such as Petunia, Browallia and Lycianthes, the source of psychoactive alkaloids, Datura, Mandragora (mandrake), and Atropa belladonna (deadly nightshade). With the exception of tobacco (Nicotianoideae) and petunia (Petunioideae), most of the economically important genera are contained in the subfamily Solanoideae. Description Solanaceae plants may take the form of herbs, shrubs, trees, or sometimes vines. The flowers are usually actinomorphic. Flower shapes are typically rotate (wheel-shaped, spreading in one plane, with a short tube) or tubular (elongated cylindrical tube), with four or five petals that are usually fused. Leaves are alternate. The fruit has axile placentation and is a berry as in the case of the tomato or wolfberry, or a dehiscent capsule as in Datura. The seeds of most Solanaceae are round and flat, about 0.079–0.16 in diameter. The stamens are epipetalous and are typically present in multiples of four or five, most commonly four or eight. The ovary is superior. Genetics Most species in the Solanaceae have 2n=24 chromosomes, but the number may be a higher multiple of 12 due to polyploidy. Wild potatoes, of which there are approximately 200, are predominantly diploid (2 × 12 = 24 chromosomes), but triploid (3 × 12 = 36 chromosomes), tetraploid (4 × 12 = 48 chromosomes), pentaploid (5 × 12 = 60) and even hexaploid (6 × 12 = 72 chromosome) species or populations exist. The cultivated species Solanum tuberosum has 4 × 12 = 48 chromosomes. Some Capsicum species have 2 × 12 = 24 chromosomes, while others have 26 chromosomes. Alkaloids Solanaceae are known for having a diverse range of alkaloids. As far as humans are concerned, these alkaloids can be desirable, toxic, or both. Tropane alkaloids One of the most important groups of these compounds is called the tropane alkaloids. The term "tropane" comes from a genus in which they are found, Atropa (the belladonna genus). Atropa is named after the Moirai, Atropos, who cut the thread of life. This nomenclature reflects its toxicity and lethality. Tropane alkaloids are also found in the Datura, Mandragora, and Brugmansia genera, as well as many others in the Solanaceae family. Chemically, the molecules of these compounds have a characteristic bicyclic structure and include atropine, scopolamine, and hyoscyamine. Pharmacologically, they are the most powerful known anticholinergics in existence, meaning they inhibit the neurological signals transmitted by the endogenous neurotransmitter, acetylcholine. Symptoms of overdose may include dry mouth, dilated pupils, ataxia, urinary retention, hallucinations, convulsions, coma, and death. Despite the extreme toxicity of the tropanes, they are useful drugs when administered in extremely small dosages. They can reverse cholinergic poisoning, which can be caused by overexposure to pesticides and chemical warfare agents such as sarin and VX. More commonly, they can halt many types of allergic reactions. Atropine, a commonly used ophthalmological agent, dilates the pupils and thus facilitates examination of the interior of the eye. Scopolamine is used as an antiemetic against motion sickness or for people receiving chemotherapy. Atropine has a stimulant effect on the central nervous system and heart, whereas scopolamine has a sedative effect. Other alkaloids Other classes of alkaloids can be found in Solanaceae, including steroidal alkaloids, pyrrolidines (nicotine, cuscohygrine). A notable alkaloid derived from Solanaceae is nicotine, of the pyrrolidines class, which occurs naturally in the tobacco genus Nicotiana. Like the tropanes, it acts on cholinergic neurons, but with the opposite effect (it is an agonist as opposed to an antagonist). It has a higher specificity for nicotinic acetylcholine receptors than other ACh proteins. Another class of toxic substances found in this family are the glycoalkaloids, for example solanine which has occasionally been responsible for poisonings in people who ate berries from species such as Solanum nigrum or Solanum dulcamara, or green potatoes. The chemical in chili peppers responsible for the burning sensation is capsaicin. Capsaicin affects only mammals, not birds. Pepper seeds can survive the digestive tract of birds; their fruit becomes brightly colored once its seeds are mature enough to germinate, thereby attracting the attention of birds who then distribute the seeds. Capsaicin extract is used to make pepper spray, a useful deterrent against aggressive mammals. Selected genera External links * Sol Genomics Network * Solanaceae Network - pictures of plants * Solanaceae Source - A worldwide taxonomic monograph of all species in the genus Solanum. *Solanaceae of Chile, por Chileflora * Solanaceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants: descriptions, illustrations, identification, information retrieval. http://delta-intkey.com * Solanaceae in USDA Plants Database. * Family Solanaceae Flowers in Israel Category:Plants Category:Plant species Category:Plant families Category:Plant science Category:Poisonous Plants